A 2.45 GHz power LD-MOSFET with reduced source inductance by V-groove connections

A new lateral double-diffused MOS field effect transistor (LD - MOSFET) (1) has been developed. At 2.45 GHz, it can deliver the maximum output power of 7.2 W per 11.52-mm gate width. The new structure of the LD-MOSFET with V-grooved source connections has been employed to minimize the source inductance (Ls), the gate-to-drain capacitance (Cgd) and the channel length (Leff). The V-grooves, which penetrate the P^-type epitaxial layer and reach the P⁺type substrate, are formed in the SiO2region just outside the active area. The N⁺type source regions of the LD-MOSFET are directly connected to the V-grooves with metallization. The Lshas become negligibly small because the device does not require the bonding wires for the source. The Cgdhas also become a quarter that of the VD- MOSFET with the same gate width, thanks to the small overlap between gate and drain. The short channel which is estimated to be 0.83 µm is formed by the double-diffusion at the MoSi2gate edges. The maximum output power of 7.2 W CW is obtained with 5.5 dB gain and efficiency of 25 percent at Vds = 40 V and f = 2.45 GHz.